The configuration file option monitor.SleepWhenIdle determines whether the VMkernel deschedules an idle virtual machine. By default, this option is enabled, a setting that ensures much better performance when running multiple virtual machines.

When you are running only a single virtual machine (such as for benchmarking VMware ESX Server), add the following line to the virtual machine's configuration (.cfg) file if you want to achieve the best possible performance in the virtual machine (at the expense of responsiveness in the console operating system):

monitor.SleepWhenIdle = 0